This invention relates to fabrication and testing of integrated circuit devices, and particularly to pick and place devices for assisting in processing and testing of integrated circuit devices.
Modem electronics devices, such as integrated circuits or semiconductorxe2x80x9cchipsxe2x80x9d are rapidly increasing in performance and functionality, and in production quantity, while simultaneously decreasing in size and unit cost. To increase the productivity and decrease the cost of electronic devices, it is desirable to decrease the time and cost of all operations in the production cycle.
Cost efficiency and productivity of processes performed on individual chips, such as burn-in, various test processes, binning, and the like, require precise, high-throughput handling of many chips. Traditionally, chips were transported in a container such as a magazinexe2x80x94a container typically designed to hold a row of chips placed end-to-end by sliding them one-by-one into one end of the container. Chips were removed from a magazine and separated from one another for processing, and replaced in a magazine after processing, by the force of gravity.
Chip handling systems which utilize the force of gravity to separate and transfer the electronic devices have at least two inherent disadvantages.
First, since modem electronic devices have become smaller and lighter than before, an individual electronic device may not have sufficient weight to be efficiently separated from the others by gravity. This may cause jamming. If such jamming occurs, it is usually necessary to stop the operation of the system to clear the jam, thus causing a serious loss of time and efficiency. Furthermore, the risk of jamming is greatly increased due to the configuration of the new types of electronic devices, such as chips with leads (pins) on all sides of the package, instead of two opposing sides as in the conventional dual in-line package (DIP).
Second, to minimize jamming, the outer surface of the electronic device must be made sufficiently smooth so as to not cause any friction or unwanted engagement with other devices or the magazine. However, this is also impractical since the plastic molded packages of the devices often have some burrs remaining from the production process and it is not generally economically practical to completely eliminate such burrs.
More recently, trays holding arrays of chips have been used for transport and handling of chips instead of magazines. The individual chips occupy individual cells within the array, and are removed from and replaced in the tray by axe2x80x9cpick and placexe2x80x9d device. A pick and place device typically employs multiple individual vacuum grippers, arranged in a row, to pick up and to place a row or column of chips. The pitch or spacing between the cells in the array is typically fixed, although the pitch may vary between different tray types. Also, the chips may have to be transported from one tray or other holder, such as a precisor, multi-track chip runway or the like, to another holder having a different pitch. This may occur as part of a processing, testing, or packaging operation or the like.
Some pick and place devices with multiple grippers have grippers positioned at a fixed pitch. The pitch of such devices may match the required pitch of an associated machine or process, or of a tray for such machine or process. However, a fixed-pitch pick and place device may often not match the pitch, of a tray or other type of chip holder, with which it must be used. In particular, where a tray or other chip holder does not match the pitch of a precisor, a multi-track runway, or any other chip holder to which the chips must be transferred, a fixed-pitch pick and place device will be mismatched to at least one of the chip holders. This results in the pick and place device having to pick-up or set-down a row of chips one at a time rather than simultaneously.
Variable-pitch pick and place devices have been developed, such as the device disclosed in U.S. Pat. No. 5,290,134, to provide the capability of simultaneous pick-up and deposit even where the pitch of one holder may differ from that of another holder. Nevertheless, a need exists for improved variable pitch pick and place devices.
A variable-pitch pick and place device with increased positioning precision and increased flexibility, with decreased complexity and cost and maintenance requirements, and with provision for electronic and thus easily-programmable pitch control is provided by the various aspects and embodiments of the present invention.
According to one embodiment, a variable-pitch pick and place device includes a plurality of device-gripping mechanisms supported in a horizontal row, the horizontal positions of the mechanisms being electronically controlled so as to maintain uniform, though variable, spacing or pitch between the device-gripping mechanisms. The desired pitch may be set via a look-up table stored in a controller such as a computer. An operator may select a tray type, or a machine or process type or the like, to trigger a look-up operation in the look-up table to obtain a value used to control the pitch. The computer may then use the value from the table to cause the adjustment of the pitch between the grippers to match a desired pitch. A controller or computer may also be used to control the pitch regardless of whether information on the desired pitch and/or the value used to control the grippers is obtained from a look-up table, entered manually, or calculated, or obtained by other means.
According to another embodiment, a variable-pitch pick and place device has a mechanical linkage, such as a scissors or pantograph linkage, itself linked to a plurality of device-gripping mechanisms so as to maintain uniform, though variable, spacing or pitch between the device-gripping mechanisms. The links to the plurality of device-gripping mechanisms are positioned so as to allow an increased number of device-gripping mechanisms to be positioned along the pantograph linkage relative to the number of links in the linkage. This yields improved positioning precision and decreased total number of linkage parts in the device.
According to yet another embodiment, a variable-pitch pick and place device has mechanical linkage such as a scissors or pantograph linkage, itself linked to a plurality of device-gripping mechanisms so as to keep uniform, though variable, spacing between the device-gripping mechanisms, and also linked to a supporting structure, the link between the linkage and the supporting structure not being at an end of the linkage, but desirably being within the middle third and most desirably at the middle of the linkage.
According to another aspect of an embodiment, a variable-pitch pick and place device may have a mechanical linkage, itself linked to a plurality of device-gripping mechanisms so as to keep uniform, though variable, spacing between the device-gripping mechanisms, and the position of the linkage may be controlled through three links to the linkage, one relatively near the middle compared to the other two, and two relatively near the ends, compared to the one.
According to another embodiment, in a device having a mechanical linkage such as a scissors or pantograph linkage for keeping uniform, though variable, spacing between electronic device-gripping mechanisms, the extension and contraction of the linkage is controlled by a timing belt or, if desired, a chain. The belt may be a continuous loop, the loop having two sides defined between a drive pulley or sprocket and an idler pulley. One end of the linkage may be attached to one side of the belt, the other end to the other. The linkage may also be anchored horizontally at the center thereof, such that the linkage is controlled from three points, providing improved position control due to decreased stack-up of mechanical tolerances. A servo or the like may be used to control the motion of the drive pulley. An encoder on the shaft of the servo motor can allow precise electronic control of the pitch of the electronic device gripping mechanisms. Such electronic control lends itself to programmed or otherwise automated pitch changes. As an aspect of the embodiment, the pitch of the grippers may be controlled using a programmed computer.
According to another embodiment, movable portions of device-gripping mechanisms are supplied with both vacuum and electrical ground via a single structure, such as an electrically conductive vacuum tube, eliminating the need for separate grounding wires for every such movable portion.
The invention is directed to these and other new and nonobvoius aspects, both individually and in combination, of improved variable-pitch pick and place apparatuses as disclosed herein. The above and other aspects, features, advantages, and benefits of the present invention will be apparent from the description bellow, which proceeds with reference to following figures: